It is known that the oxides and carbonates of a number of elements, and particularly Group IIA elements, have catalytic properties. The catalytic properties are particularly useful for the oxidative coupling of methane to form higher hydrocarbons. These oxides and carbonates may be used as fixed bed catalysts or as fluidised bed catalysts. In the former case a stream of gas containing the reactant molecules is caused to flow past a stationary bed of catalyst particles. In the latter case the particles are constantly mobile within an upflowing stream of the reactant gas. This movement causes abrasion and spalling of the catalyst particles. The resulting dust can then be carried out of the fluidised bed reactor in the gas stream.
For many large scale operations fluidised bed reactors are preferred, however carbonate catalysts, and particularly Group IIA carbonate catalysts, are relatively soft and are therefore not suitable for use in fluidised bed reactors.